Analog Mux

Discussion in 'Analog & Mixed-Signal Design' started by sharanbr123, Oct 20, 2014.

  1. sharanbr123

    Thread Starter Member

    Sep 29, 2014
    49
    0
    Hello All,

    I would like to know if there is something called analog mux.

    Also, I would like to understand for the following example below which method (1 or 2) would be more efficient ... I would like to monitor certain analog inputs to the design. The monitor application itself is in digital domain. Hence the analog signal has to be brought into digital domain first. There are 8 such analog signals which need similar monitoring

    1) I will put a ADC for every analog signal and then do necessary processing
    2) I will (analog) multiplex the 8 analog signals and then put a single ADC

    In the first case, we have 8 ADC while in the second case, we have one analog mux followed by 1 ADC.
    I am not sure which is more efficient and whether analog mux is even realizable at all.

    I would like experts to weigh-in ...
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    Yes. mux = "multiplexer"

    Both methods are used. Which is best depends on speed and complexity.

    For high speed, (such as audio) best to have a separate ADC for each analog. Because after selecting with an analog multiplexer the signal needs to settle before being converted. The delay would be too long for audio.

    For slower signals (temperature sensors, etc) it is normal to have an analog multiplexer and a single ADC.
     
  3. sharanbr123

    Thread Starter Member

    Sep 29, 2014
    49
    0
    Hello JDT,

    Thanks. Primarily, I wanted to know if the cost (in terms of complexity) of adding an analog muxtiplexer is higher than adding individual ADC's.
    In such a scenario, it is probably good to go with individual ADC. In other words, how does complexity of an analog mux compare with ADC?
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    check CD4051 or reed relay.
     
  5. MrChips

    Moderator

    Oct 2, 2009
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  6. crutschow

    Expert

    Mar 14, 2008
    12,981
    3,221
    Generally the cost of the Mux and one ADC is less then the alternate due to fewer parts required. But there are ADC's available with multiple ADC's in one package or with built-in multiplexers, so the price of using one of those could be comparable or even less. It really depends upon the application.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,984
    3,725
    Microcontrollers (PIC) normally have an ADC with several ADC channels (essentially an on-board multiplexer). This is probably your lowest cost option if the ADC has the resolution you need (10 or 12 bits usually). Some PICs have more than 10 channels to feed the ADC. Simply set on on-board register with software to select your ADC channel.
     
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